I. Field of the Invention:
This invention relates generally to electromechanical switching apparatus and more particularly to a four quadrant touch pad useful in generating control signals for a motor or other electrical or electronic devices for moving or positioning an imager or object.
II. Discussion of the Prior Art:
Various electromechanical devices are known in the art for effecting steering of an image or object by producing control signals in accordance with the manner in which the device in question is manipulated. For example, so-called "joy-sticks" are frequently used with computing equipment to cause movement of a cursor or other image on the face of a CRT monitor. A typical joy-stick operates by producing control signals by means of electrical potentiometers linked to the movable actuating rod where the magnitude of the signal determines rate of motion and the polarity of the signal signifies direction, e.g., up, down, left and right.
Another well-known device is the so-called "track-ball". In this arrangement, a spherical member is journaled for rotation about any axis within a socket and a portion of the spherical surface of the ball projects outwardly from the socket. By suitable rotation of the ball, control signals are developed for directing the motion of an image or an object depending upon the equipment with which the track-ball device is used.
Another known device is the so-called "touch pad". In known prior art arrangements, a printed circuit board having a pattern of conductors formed in a grid of a predetermined spacing is juxtaposed with a flexible plastic insulating layer having a pattern of metallization on the under surface thereof. A spacer layer may be disposed between the two. By depressing the flexible layer against the underlying printed circuit grid, signals are produced which are directly related to the particular point on the pad where it is being touched.
One problem with the above-described prior art devices is that they are subject to failure due to mechanical wear. Moreover, in the case of the diaphragm-type touch pad mentioned above, within a short time, the flexible outer layer may be permanently distorted, rendering the device inoperable.